APA (7th ed.) Citation

United States. Postmaster General. (1927). Precanceled stamps must be defaced. U.S. GPO.

Chicago Style (17th ed.) Citation

United States. Postmaster General. Precanceled Stamps Must Be Defaced. Washington: U.S. GPO, 1927.

MLA (9th ed.) Citation

United States. Postmaster General. Precanceled Stamps Must Be Defaced. U.S. GPO, 1927.

Warning: These citations may not always be 100% accurate.